1. Field of the Invention
The present invention relates to the field of water purifiers and, more specifically, to improved compound valves for controlling the operation of reverse osmosis water purifying systems.
2. Prior Art
U.S. Pat. No. 4,176,063 discloses a control valve for reverse osmosis water purifying systems that controls the operation of a system according to the water pressure present in the system's pure water delivery line. The control valve comprises four individual diaphragm valves linked together by hydraulic passages, two of which valves are in essence double diaphragm valves utilizing diaphragms of substantially different size with a mechanical linkage therebetween so that the desired hydraulic pressure ratios can be achieved.
One of the diaphragm valves is a check valve inserted in the pure water delivery line that maintains pressure in the line between the check valve and the spigot when the spigot is closed. Another of the diaphragm valves is a double diaphragm valve functioning as a pilot valve, hydraulically linked to the pure water delivery line such that the pilot valve opens when the pure water pressure is low, i.e. when the dispensing spigot is open. The third diaphragm valve is a squeeze water valve which opens in response to opening of the pilot valve and controls the flow of pressurized waste water from the reverse osmosis unit to a pure water tank in which the pure water is maintained in a bladder. The pressurized waste water is used to pressurize the pure water to provide adequate pure water delivery pressure when the spigot is open. Finally the fourth diaphragm valve, also a double diaphragm valve to get the desired area ratios, is an inlet water valve which controls the inflow of water from the main water line to the system. This inlet valve is closed when the pure water tank is completely filled with pure water, thus cutting off the flow of waste water when not needed.
This prior art control valve has subsequently been improved by the addition of two additional valves. The first of these, a duck bill valve, assures that there is always a limited flow of waste water through the reverse osmosis unit to remove salts and other impurities from the unit's filter membrane whenever water is being filtered, a function provided by a separate constriction elsewhere in the system in accordance with the disclosure of the '063 Patent. The second additional valve, a diverter valve, allows squeeze water in the pure water tank to flow to a drain to eliminate the back pressure in the pure water during the filtering process.
The prior art control valve, particularly as improved, functions very well for the intended purpose. The double diaphragm valves, however, having a mechanical linkage therebetween, tend to make the overall assembly relatively large, with much of the complexity thereof being associated with these double diaphragm valves and the mechanical linkage therebetween. Further, as shown in the '063 Patent and as in actual equipment manufactured and sold in accordance with the patent, one of the two diaphragms for each of the double diaphragm valves was a flat sheet rubber deflectable upward or downward, as conditions dictated. Because of the lack of convolutions therein, the diaphragm deflection of these flat diaphragms also creates substantially radial tension and sharp deflections adjacent the regions of support of the diaphragms, thereby encouraging failure thereof by cracking, etc. Also, because of the lack of peripheral sealing ring on the flat sheet diaphragms, leakage of water from the valve assembly, when it occurred, frequently would be associated with the flat diaphragms and the difficulties in attempting to obtain a good seal by the mere clamping of the peripheral edge thereof. Obviously, these flat diaphragms and the associated support thereof could be modified to allow the use of convoluted diaphragms having a peripheral seal ring thereon to improve the reliability thereof, though the additional diaphragm and the mechanical separator for the two diaphragms in each of the two double diaphragm valves still would add substantially to the size, complexity and cost of the valve assembly over that of the present invention.